Kei Cars are a Japanese phenomena which sets very strict rules for cars to comply with. They include dimensions and engine size and are quite popular in Japan as they are, from what I understand, the only type of car you can own for which you do not need to proof you have a parking spot. In the nineties most Japanese manufacturers wanted to offer their customers something fancier then the normal "box on wheels" these dimensions almost seemed to dictate. Aoshima has reproduced these in 1:64th scale in a series of 4 different models and 3 colours each, making the series 12 cars big. I got two of the casts some years ago and only recently was I able to complete the set. I did not bother collecting all the colour variations.
Autozam AZ-1 (Mazda)
And my latest additions: